Methods of forming a ferroelectric memory cell

ABSTRACT

A method of forming a ferroelectric memory cell. The method comprises forming an electrode material exhibiting a desired dominant crystallographic orientation. A hafnium-based material is formed over the electrode material and the hafnium-based material is crystallized to induce formation of a ferroelectric material having a desired crystallographic orientation. Additional methods are also described, as are semiconductor device structures including the ferroelectric material.

TECHNICAL FIELD

Embodiments of the disclosure relate to the field of semiconductordevice design and fabrication. More specifically, embodiments of thedisclosure relate to methods of forming a ferroelectric (FE) memory cellincluding a FE material on an electrode material, and to relatedsemiconductor device structures.

BACKGROUND

Lead zirconate titanate (PZT) has been investigated as a FE material foruse in non-volatile data storage, such as FE Random Access Memory(FERAM). However, PZT is not compatible with conventional semiconductorprocessing techniques and is not scaleable because the PZT loses its FEproperties at lower thicknesses and, therefore, has integration issues.

Hafnium silicate (HfSiO_(x)) is a high-k dielectric material and hasbeen investigated as a replacement ferroelectric material for PZT.Hafnium silicate is polymorphic and may form in monoclinc, tetragonal,cubic, or orthorhombic crystal structures, with each of the crystalstructures having multiple possible crystallographic orientations, suchas the (111) or (200) crystallographic orientations. Hafnium silicate isconventionally formed with the (111) crystallographic orientation beingthe dominant formed crystallographic orientation.

Titanium nitride is a polymorphic material and may form many crystalstructures, with each crystal structure having multiple possiblecrystallographic orientations, such as the (001), (002), (100), (110),(111), or (200) crystallographic orientations. Titanium nitride isconventionally formed in the cubic phase and has multiplecrystallographic orientations, with the (200) crystallographicorientation often being the dominant formed crystallographicorientation.

It would be desirable to have improved methods of forming hafniumsilicate or other FE materials, such that a desired crystallographicorientation of the ferroelectric material can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of a semiconductor devicestructure in accordance with an embodiment of the present disclosure;

FIG. 2 shows the crystallographic orientations of TiN formed by anAtomic Layer Deposition (ALD) process and TiN formed by a conventionalSequential Flow Deposition (SFD) process, as measured by grazingincidence x-ray diffraction (GIXRD);

FIGS. 3 and 4 are micrographs showing the roughness of TiN formed by anALD process compared to that of TiN formed by the SFD process;

FIG. 5 shows the crystallographic orientations of hafnium silicate, asmeasured by GIXRD, for a test wafer and a control wafer;

FIG. 6 is a Positive Up Negative Down (PUND) hysteresis conducted at 100cycles for the test wafer and control wafer; and

FIG. 7 is a plot of median 2Pr (remanent polarization, which is the sumof the magnitudes of the positive and negative polarization at E=0) as afunction of cycle number for the test wafer and control wafer.

DETAILED DESCRIPTION

Methods of forming a ferroelectric memory cell are disclosed, as arerelated semiconductor device structures including a ferroelectricmaterial and an electrode material. The ferroelectric material may becrystallized in a desired crystallographic orientation. The desiredcrystallographic orientation of the ferroelectric material may beachieved by forming the electrode material at a desired crystallographicorientation, forming a hafnium-based material over the electrodematerial, and crystallizing the hafnium-based material to produce aferroelectric material. Thus, the electrode material may function as atemplate to induce formation of the desired crystallographic orientationof the ferroelectric material.

The following description provides specific details, such as materialtypes, material thicknesses, and processing conditions in order toprovide a thorough description of embodiments of the disclosure.However, a person of ordinary skill in the art will understand that theembodiments of the disclosure may be practiced without employing thesespecific details. Indeed, the embodiments of the disclosure may bepracticed in conjunction with conventional fabrication techniquesemployed in the industry. In addition, the description provided hereindoes not form a complete process flow for forming a semiconductor devicestructure, and each of the semiconductor device structures describedbelow do not form a complete semiconductor device. Only those processacts and structures necessary to understand the embodiments of thedisclosure are described in detail below. Additional acts to form acomplete semiconductor device may be performed by conventionalfabrication techniques. Also note, any drawings accompanying the presentapplication are for illustrative purposes only, and are thus not drawnto scale. Additionally, elements common between figures may retain thesame numerical designation.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise.

As used herein, relational terms, such as “first,” “second,” “top,”“bottom,” “upper,” “lower,” “over,” “under,” etc., are used for clarityand convenience in understanding the disclosure and accompanyingdrawings and do not connote or depend on any specific preference,orientation, or order, except where the context clearly indicatesotherwise.

As used herein, the term “substrate” means and includes a foundationmaterial or construction upon which components, such as those within asemiconductor device structure are formed. The substrate may be asemiconductor substrate, a base semiconductor material on a supportingstructure, a metal electrode, or a semiconductor substrate having one ormore materials, structures, or regions formed thereon. The substrate maybe a conventional silicon substrate or other bulk substrate including asemiconductive material. As used herein, the term “bulk substrate” meansand includes not only silicon wafers, but also silicon-on-insulator(“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates orsilicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on abase semiconductor foundation, or other semiconductor or optoelectronicmaterials, such as silicon-germanium (Si_(1-x)Ge_(x), where x is, forexample, a mole fraction between 0.2 and 0.8), germanium (Ge), galliumarsenide (GaAs), gallium nitride (GaN), or indium phosphide (InP), amongothers. Furthermore, when reference is made to a “substrate” in thefollowing description, previous process stages may have been utilized toform materials, regions, or junctions in or on the base semiconductorstructure or foundation.

As used herein, the term “ferroelectric” means and includes a materialhaving a spontaneous electric polarization (electric dipole) that can bereversed in the presence of an electric field.

As used herein, the term “dominant” in reference to a crystallographicorientation of a material means and includes a material exhibiting aspecified crystallographic orientation at a relatively greater amountthan any other crystallographic orientation. By way of non-limitingexample, a “dominant (111) crystallographic orientation” means thematerial exhibits the (111) crystallographic orientation at a greateramount than any other crystallographic orientation.

As used herein, the term “hafnium silicate” means and includes amaterial including hafnium, silicon, and oxygen atoms. For convenience,the composition of the material may be abbreviated by “HfSiO_(x),” whichdoes not indicate the stoichiometry of the hafnium, silicon, and oxygenatoms.

As used herein, the term “hafnium aluminate” means and includes amaterial including hafnium, aluminum, and oxygen atoms. For convenience,the composition of the material may be abbreviated by “HfAlO_(x),” whichdoes not indicate the stoichiometry of the hafnium, aluminum, and oxygenatoms.

As used herein, the term “hafnium zirconate” means and includes amaterial including hafnium, zirconium, and oxygen atoms. Forconvenience, the composition of the material may be abbreviated by“HfZrO_(x),” which does not indicate the stoichiometry of the hafnium,zirconium, and oxygen atoms.

As used herein, the term “strontium-doped hafnium oxide” means andincludes a material including hafnium, strontium, and oxygen atoms. Forconvenience, the composition of the material may be abbreviated by“HfSrO_(x),” which does not indicate the stoichiometry of the hafnium,strontium, and oxygen atoms.

As used herein, the term “magnesium-doped hafnium oxide” means andincludes a material including hafnium, magnesium, and oxygen atoms. Forconvenience, the composition of the material may be abbreviated by“HfMgO_(x),” which does not indicate the stoichiometry of the hafnium,magnesium, and oxygen atoms.

As used herein, the term “gadolinium-doped hafnium oxide” means andincludes a material including hafnium, gadolinium, and oxygen atoms. Forconvenience, the composition of the material may be abbreviated by“HfGdO_(x),” which does not indicate the stoichiometry of the hafnium,gadolinium, and oxygen atoms.

As used herein, the term “yttrium-doped hafnium oxide” means andincludes a material including hafnium, yttrium, and oxygen atoms. Forconvenience, the composition of the material may be abbreviated by“HfYO_(x),” which does not indicate the stoichiometry of the hafnium,yttrium, and oxygen atoms.

FIG. 1 illustrates a semiconductor device structure 100 having asubstrate 102, an electrode 104 over the substrate 102, a FE material106 over the electrode 104, another electrode 108 over the FE material106, and a metal silicide material 110 over the another electrode 108.The electrode 104 may be formed from a crystalline material, such astitanium nitride, having a desired dominant crystallographicorientation, such as a dominant (111) crystallographic orientation.Thus, if the electrode material is titanium nitride, the electrodematerial may include a greater amount of the (111) crystallographicorientation of titanium nitride than other crystallographic orientationsof titanium nitride, i.e., (001), (002), (100), (110), (200), (311),(331), (420), (422), or (511) crystallographic orientations. Whileexamples herein describe that the electrode 104 is formed of TiN, othermaterials may be used as long as the material of the electrode 104 has adesired crystallographic orientation that is configured to produce thedesired crystallographic orientation of the FE material 106.

The semiconductor device structure 100 may be configured as a memorycell of a FERAM. The memory cells may, for example, be arrayed in a 1transistor/1 capacitor (1T/1C) configuration. However, otherconfigurations of the memory cells may also be used. Additional acts toform a complete FERAM including the semiconductor device structure 100of FIG. 1 may be performed by conventional fabrication techniques, whichare not described in detail herein.

The FE material 106 may be a metal oxide material, such as ahafnium-based material, that includes a dopant. The hafnium-basedmaterial is crystallized to form the FE material 106. For simplicity andconvenience, the term “hafnium-based material” is used herein to referto the material before the material is crystallized and the term “FEmaterial” is used to refer to the material after the material iscrystallized. The FE material 106 may be hafnium oxide into which thedopant is incorporated. The dopant may be an element such as silicon,aluminum, zirconium, magnesium, strontium, gadolinium, yttrium, otherrare earth elements, or combinations thereof. Examples of ferroelectricmaterials include, but are not limited to, hafnium silicate (HfSiO_(x)),hafnium aluminate (HfAlO_(x)), hafnium zirconate (HfZrO_(x)),strontium-doped hafnium oxide (HfSrO_(x)), magnesium-doped hafnium oxide(HfMgO_(x)), gadolinium-doped hafnium oxide (HfGdO_(x)), yttrium-dopedhafnium oxide (HfYO_(x)), or combinations. While hafnium oxide does notexhibit ferroelectric properties, hafnium oxide in crystalline form andincluding one of the above-mentioned dopants may be ferroelectric.Hafnium oxide in crystalline form and including one of theabove-mentioned dopants at the correct composition is ferroelectric. TheFE material 106 may include from 0.1 mol % to about 70 mol % of thedopant. If the FE material 106 is HfSiO_(x), the FE material 106 may behafnium oxide including from about 4 mol % to about 6 mol % silicon,such as from about 4.4 mol % to about 5.6 mol % silicon. In oneembodiment, the HfSiO_(x) material includes 4.7 mol % silicon. If the FEmaterial 106 is HfAlO_(x), the FE material 106 may be hafnium oxideincluding from about 5 mol % to about 7 mol % aluminum. If the FEmaterial 106 is HfYO_(x), the FE material 106 may be hafnium oxideincluding from about 2.5 mol % to about 5.5 mol % yttrium. If the FEmaterial 106 is HfZrO_(x), the FE material 106 may be hafnium oxideincluding from about 40 mol % to about 70 mol % zirconium. The FEmaterial 106 of the semiconductor device structure 100 may be in acrystalline state and have a desired crystallographic orientation.

The another electrode 108 may be formed of titanium nitride (TiN) in acrystalline state. The material of the another electrode 108 is notlimited to a specific crystallographic orientation and, thus, may beformed from crystalline TiN in a (001), (002), (100), (110), (111), or(200) crystallographic orientation, or combinations thereof. The anotherelectrode 108 may be formed of titanium nitride having the same or adifferent dominant crystallographic orientation as the electrode 104.While examples herein describe that the another electrode 108 is formedof TiN, other conventional materials may be used.

The metal silicide material 110 may be tungsten silicide (WSi_(x)) orother metal silicide. The metal silicide material 110 may be positionedover the another electrode 108 and the FE material 106. The metalsilicide material 110 may prevent deterioration, such as oxidation, ofthe another electrode 108 during fabrication of the semiconductor devicestructure 100.

In one embodiment, the electrode 104 is formed of TiN in the dominant(111) crystallographic orientation, the FE material 106 is hafniumsilicate in the dominant (200) crystallographic orientation, the anotherelectrode material 106 is formed from TiN, and the metal silicidematerial 110 is tungsten silicide.

Accordingly, the present disclosure describes a FE memory cell thatcomprises an electrode comprising titanium nitride in a dominant (111)crystallographic orientation over a substrate. A ferroelectric materialis over the electrode and another electrode material is over theferroelectric material.

To form the semiconductor device structure 100, the electrode 104exhibiting the desired dominant crystallographic orientation may beformed on the substrate 102 by appropriately selecting the electrodematerial and the formation conditions. For instance, the electrode 104may be formed by depositing (111) crystallographic orientation titaniumnitride over the substrate 102. In one embodiment, the (111)crystallographic orientation titanium nitride of the electrode 104 isformed by depositing titanium nitride by ALD, using an organometallicALD precursor. The organometallic ALD precursor may include, but is notlimited to, tetrakis-dimethylamino titanium (TDMAT). However, otherorganometallic ALD precursors may be used. ALD techniques for formingTiN are known in the art and, therefore, are not described in detailherein. Since the organometallic ALD precursor is free of chlorine, theresulting TiN has a low chlorine content, which reduces shielding andresults in uniform electric fields in the electrode 104. The electrode104 may be formed as a continuous material, such as at a thicknessranging from about 20 Å to about 200 Å, from about 50 Å to about 130 Å,or from about 40 Å to about 70 Å. In one embodiment, the electrode 104thickness is about 60 Å.

While an ALD method of forming the electrode 104 from TiN using aspecific ALD precursor is described herein, other methods of forming theelectrode 104 may be used, as long as the resulting electrode 104 hasthe desired dominant crystallographic orientation, i.e., TiN in thedominant (111) crystallographic orientation. For instance, the electrode104 with the desired dominant crystallographic orientation mayalternatively be formed by depositing titanium nitride using TiAlN or bydepositing titanium nitride using a titanium tetrachloride (TiCl₄)precursor and ammonia (NH₃). Process conditions for these othertechniques may be selected such that the TiN of the electrode 104 isformed in the dominant (111) crystallographic orientation.

The hafnium-based material of the FE material 106 may be formed over theelectrode 104. The hafnium-based material may include the hafnium oxidematerial with the dopant, as previously described. The hafnium-basedmaterial may be formed by conventional techniques, such as sputtering,ALD, CVD, PECVD, or MOCVD, which are not described in detail herein.Since the metal oxide material is not ferroelectric as formed, the molarconcentration of the dopant in the metal oxide material may be tailoredto provide the metal oxide material with ferroelectric properties. Themolar concentration of the dopant in the metal oxide material may becontrolled by appropriately selecting the relative ratios of metalprecursor, oxygen precursor, and dopant precursor used and by varyingthe number of cycles conducted. The hafnium-based material, in itsinitial, as-formed state, may be an amorphous material.

The electrode material of the another electrode 108 may be formed overthe hafnium-based material of the FE material 106. The electrodematerial of the another electrode 108 may be formed by conventionaltechniques, which are not described in detail herein. In one embodimentwhere the electrode material of the another electrode 108 is TiN, theTiN may be formed by a conventional Sequential Flow Deposition (SFD)process using TiCl₄ and NH₃. If both the electrode 104 and the anotherelectrode 108 are formed from TiN, the TiN of the another electrode 108may have the same, or a different, crystallographic orientation as theelectrode 104. The electrode 104, the hafnium-based material of the FEmaterial 106, and another electrode 108 may form a metal-insulator-metal(MIM) stack 112. During the formation of the another electrode 108, thehafnium-based material of the FE material 106 may remain in itsamorphous state.

After forming the hafnium-based material of the FE material 106 and theanother electrode 108, the MIM stack 112 may be subjected to an annealprocess to crystallize the hafnium-based material into its desiredcrystallographic orientation. The annealing conditions may be determinedbased on the composition of the hafnium-based material and the thicknessof the electrodes 104, 108. The crystallization temperature of thehafnium-based material may be a function of the amount of dopant presentin the hafnium-based material. At relatively higher dopantconcentrations, the crystallization temperature of the hafnium-basedmaterial may be higher than the crystallization temperature of thehafnium-based material having a lower amount of the dopant. Thecrystallization temperature of the hafnium-based material may range fromabout 800° C. to about 1000° C. By appropriately forming the electrode104 having the desired dominant crystallographic orientation andfollowing the anneal, the hafnium-based material may crystallize intoits desired crystallographic orientation. By way of example, if theelectrode 104 is formed from (111) crystallographic orientation TiN andthe hafnium-based material of the FE material 106 is formed from hafniumsilicate having 4.7 mol % silicon, following the anneal, the FE material106 has an orthorhombic crystal structure with a dominant (200)crystallographic orientation. The (111) crystallographic orientationtitanium nitride of the electrode 104 may provide a smooth surface thatfunctions as a template for forming the dominant (200) crystallographicorientation of the hafnium silicate used as the FE material 106. If amaterial other than hafnium silicate is used as the hafnium-basedmaterial of the FE material 106, following the anneal process the FEmaterial 106 may have an orthorhombic crystal structure. However, theresulting dominant crystallographic orientation of the FE material 106may be a crystallographic orientation other than the (200)crystallographic orientation, depending on the hafnium-based materialused.

Additional process acts to form a FERAM including the semiconductordevice structure 100 of the present disclosure may be performed byconventional fabrication techniques, which are not described in detailherein.

Accordingly, the present disclosure also includes a method of forming aferroelectric memory cell. The method comprises forming an electrodematerial exhibiting a desired dominant crystallographic orientation. Ahafnium-based material is formed over the electrode material and thehafnium-based material is crystallized to induce formation of aferroelectric material having a desired crystallographic orientation.

The present disclosure includes another method of forming aferroelectric memory cell. The method comprises forming an electrodematerial comprising titanium nitride in a dominant (111)crystallographic orientation. An amorphous hafnium silicate material isformed over the electrode material. Another electrode material is formedover the amorphous hafnium silicate material and the amorphous hafniumsilicate material is crystallized to induce formation of a dominant(200) crystallographic orientation.

During use and operation, the semiconductor device structure 100 of thepresent disclosure may exhibit improved cell performance. Thesemiconductor device structure 100 where the FE material 106 has thedesired crystallographic orientation on the electrode 104 having thedesired dominant crystallographic orientation exhibited intrinsicallyimproved ferroelectric properties, such as improved cycling, improveddata retention, lower ferroelectric coercivity (E_(c)), and lowerelectrical field saturation.

Without being bound by any theory, it is believed that by forming theelectrode 104 having the desired dominant crystallographic orientation,the desired crystallographic orientation of the hafnium-based materialof the ferroelectric material 106 may be formed. By forming theferroelectric material 106 having the desired crystallographicorientation, the dipole mechanism of the ferroelectric material 106 maybe oriented perpendicular to the electrodes 104, 108. For instance, thedominant (111) crystallographic orientation of TiN is believed to besmoother than any other crystallographic orientation of TiN. Thedominant (111) crystallographic orientation of TiN is believed tofunction as a smooth template upon which the (200) crystallographicorientation of the hafnium-based material of the ferroelectric material,such as HfSiO_(x), may be formed. In a FERAM cell having the electrode104 formed of the dominant (111) crystallographic orientation of TiN andthe FE material 106 formed of HfSiO_(x) in the (200) crystallographicorientation, the dipole of the ferroelectric material 106 is orientedperpendicular to the electrodes 104, 108. Thus, the FERAM cell can beeasily polarized and operated along its c axis.

The following examples serve to explain embodiments of the presentinvention in more detail. These examples are not to be construed asbeing exhaustive or exclusive as to the scope of the present disclosure.

EXAMPLES Example 1

A 150 Å layer of titanium nitride was formed by a conventionalSequential Flow Deposition (SFD) process using TiCl₄ and NH₃. Another150 Å layer of titanium nitride was formed by an ALD process using TDMATas the ALD precursor. The crystal structures and crystallographicorientation of the TiN materials was determined by grazing incidencex-ray diffraction (GIXRD) analysis. The crystal structures of both TiNmaterials were polycrystalline cubic. However, the both materials haddifferent crystallographic orientations. As shown in FIG. 2, the TiNformed by the ALD process had a dominant (111) crystallographicorientation with smaller peaks at the (200) and (220) crystallographicorientations, while the TiN formed by the SFD process had a dominant(200) crystallographic orientation with minor peaks at the (111) and(220) crystallographic orientations. In the TiN formed by the SFDprocess, the (200) crystallographic orientation was parallel ornear-parallel to the substrate's surface, while in the TiN formed by theALD process, the (111) crystallographic orientation was parallel ornear-parallel to the substrate's surface.

The roughness of the two titanium nitride materials was also different.The roughness of the materials was measured by conventional atomic forcemicroscopy (AFM) techniques. As shown in FIGS. 3 and 4, the TiN formedby the ALD process was significantly smoother than the TiN formed by theSFD process. The TiN formed by the ALD process had a root-mean-square(RMS) roughness of 4.0 A while the TiN formed by the SFD process had anRMS of 11.1 A.

Example 2

Test wafers including TiN materials formed by different techniques wereprepared. The control wafer included a polysilicon substrate, a 50 Å TiNmaterial (a bottom electrode) over the substrate, a 100 Å HfSiO_(x)material over the TiN material of the bottom electrode, a 100 Å TiNmaterial (a top electrode) over the HfSiO_(x) material, and a 600 ÅWSi_(X) over the TiN material of the top electrode. The TiN of thebottom electrode had a dominant (200) crystallographic orientation. TheHfSiO_(x) material included 4.7 mol % silicon. The TiN of the bottom andtop electrodes was formed by a conventional Sequential Flow Deposition(SFD) process using TiCl₄ and NH₃. The control wafer is referred toherein and in the drawings as wafer 5.

In the sample wafers, the TiN material of the bottom electrode wasformed to 60 Å or 125 Å by an ALD process using TDMAT as the ALDprecursor. The sample wafer having the 125 Å TiN material of the bottomelectrode is referred to herein and in the drawings as wafer 5 and the60 Å TiN material of the bottom electrode is referred to herein and inthe drawings as wafer 18. The TiN of the bottom electrode had a dominant(111) crystallographic orientation. The sample wafers included apolysilicon substrate, a 100 Å HfSiO_(x) material (including 4.7 mol %silicon) over the TiN material of the bottom electrode, a 100 Å TiNmaterial (a top electrode) over the HfSiO_(x) material, and a 600 ÅWSi_(X) over the TiN material of the top electrode. The 100 Å TiNmaterial of the top electrode was formed by a conventional SFD process.

The control and sample wafers including stack 112 of material asdescribed above were subjected to an anneal at 1000° C. Following theanneal, the HfSiO_(x) material over the TiN material formed by the ALDprocess (wafer 18) exhibited an orthorhombic crystal structure and adominant (200) crystallographic orientation, as shown in FIG. 5. Incontrast, the HfSiO_(x) material over the TiN material formed by the SFDprocess (wafer 5) exhibited a dominant (111) crystallographicorientation.

The performance of the control and sample wafers was also determined.Data retention characteristics were evaluated by a conventional PositiveUp Negative Down (PUND) pulse technique at 100 cycles. As shown in FIG.6, wafer 18 had a lower ferroelectric coercivity (E_(c)) of 1.6 V,compared to E_(c) (2.8 V) of the control wafer (wafer 5). The lowerE_(c) implies the voltage needed to operate a device including the wafer18 would be less than that for wafer 5, and a device including wafer 18can be operated at lower voltage than wafer 5. Thus, wafer 18demonstrated a much healthier ferroelectric/PUND hysteresis behaviorwith lower E_(c) and lower electrical field saturation.

FIG. 7 is a plot of median 2Pr as a function of cycle number, whereStage 1 is the initial polling state, Stage 2 is the lifetime state, andStage 3 is the degradation state. As shown in FIG. 7, wafer 18 exhibitedextended cycling before degradation compared to wafer 5 (the controlwafer). Wafer 5 showed polarization fatigue at about 1×10⁵ cycles whilewafer 18 showed an improvement of almost 1.5 orders of magnitude greater(3×10⁶ cycles) before degradation began to occur. In addition, wafer 18had an average 2Pr plateau of about 12 uC/sq cm, which is 30% memorywindow/sensing margin improvement compared with wafer 5, having anaverage 2Pr plateau of about 9 uC/sq cm. Wafer 18 also showed animprovement in initial cycling, as evidenced by the lower slope of aline (not shown) fitting the data measured during Stage 1. The initialcycling (i.e., Stage 1) of wafer 18 was more stable than that of wafer5, implying that the dipole of the FE material of wafer 18 is orientedcorrectly to the dipole of the electrodes and the resulting device isable to begin writing quickly. In contrast, wafer 5 needs additionaltime for the dipole of its FE material to align correctly with thedipole of its electrodes, which is indicated by the steep slope of theline in Stage 1. Thus, wafer 18 exhibited improved initial cycling, agreater 2Pr, and an improved extended cycling before degradationoccurred.

These results show that wafer 18 (having the orthorhombic HfSiO_(x)crystal structure and a dominant (200) crystallographic orientation onthe dominant (111) crystallographic orientation TiN) had intrinsicallyimproved ferroelectric properties, such as improved 2Pr values, improvedcycling, improved E_(c), and lower electrical field saturation, comparedto the control wafer.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, the disclosure is not intended to be limited to the particularforms disclosed. Rather, the disclosure is to cover all modifications,equivalents, and alternatives falling within the scope of the disclosureas defined by the following appended claims and their legal equivalents.

What is claimed is:
 1. A method of forming a ferroelectric memory cell,comprising: forming an electrode material comprising titanium nitride byatomic layer deposition; forming a hafnium-based material over theelectrode material; and crystallizing the hafnium-based material toinduce formation of a ferroelectric material having a desiredcrystallographic orientation.
 2. The method of claim 1, wherein formingan electrode material comprising titanium nitride by atomic layerdeposition comprises forming crystalline titanium nitride.
 3. The methodof claim 1, wherein forming an electrode material comprising titaniumnitride by atomic layer deposition comprises forming titanium nitride ina dominant (111) crystallographic orientation.
 4. The method of claim 3,wherein forming titanium nitride in a dominant (111) crystallographicorientation comprises forming the titanium nitride in the dominant (111)crystallographic orientation using an organometallic precursor.
 5. Themethod of claim 3, wherein forming titanium nitride in a dominant (111)crystallographic orientation comprises forming the titanium nitride inthe dominant (111) crystallographic orientation using titaniumtetrachloride and ammonia.
 6. The method of claim 3, whereincrystallizing the hafnium-based material comprises forming orthorhombichafnium silicate over the titanium nitride in the dominant (111)crystallographic orientation.
 7. The method of claim 3, whereincrystallizing the hafnium-based material comprises forming hafniumsilicate in a dominant (200) crystallographic orientation over thetitanium nitride in the dominant (111) crystallographic orientation. 8.The method of claim 3, wherein forming hafnium silicate over thetitanium nitride in the dominant (111) crystallographic orientationcomprises forming hafnium silicate in a dominant (200) crystallographicorientation over the titanium nitride in the dominant (111)crystallographic orientation.
 9. The method of claim 1, wherein forminga hafnium-based material over the electrode material comprises formingan amorphous hafnium-based material over the electrode material.
 10. Themethod of claim 1, wherein forming a hafnium-based material over theelectrode material comprises forming hafnium silicate, hafniumaluminate, hafnium zirconate, strontium-doped hafnium oxide,magnesium-doped hafnium oxide, gadolinium-doped hafnium oxide,yttrium-doped hafnium oxide, or combinations thereof over the electrodematerial.
 11. The method of claim 1, wherein crystallizing thehafnium-based material comprises annealing the hafnium-based material.12. A method of forming a ferroelectric memory cell, comprising: formingan electrode material comprising titanium nitride in a dominant (111)crystallographic orientation; forming an amorphous hafnium silicatematerial over the electrode material; forming another electrode materialover the amorphous hafnium silicate material; and crystallizing theamorphous hafnium silicate material to induce formation of a dominant(200) crystallographic orientation of the hafnium silicate.
 13. Themethod of claim 12, wherein forming an electrode material comprisingtitanium nitride in a dominant (111) crystallographic orientationcomprises forming the titanium nitride by an atomic layer depositionprocess.
 14. The method of claim 12, wherein crystallizing the amorphoushafnium silicate material to induce formation of a dominant (200)crystallographic orientation of the hafnium silicate comprises exposingthe amorphous hafnium silicate material to a temperature greater thanabout 800° C.
 15. The method of claim 12, wherein forming anotherelectrode material over the amorphous hafnium silicate materialcomprises forming titanium nitride over the amorphous hafnium silicatematerial.
 16. A method of forming a ferroelectric memory cell,comprising: forming a titanium nitride material comprising forming thetitanium nitride in a dominant (111) crystallographic orientation byatomic layer deposition; forming an amorphous hafnium-based materialover the titanium nitride material; and crystallizing the amorphoushafnium-based material to induce formation of a dominantcrystallographic orientation.
 17. The method of claim 16, whereinforming an amorphous hafnium-based material over the titanium nitridematerial comprises forming hafnium silicate, hafnium aluminate, hafniumzirconate, strontium-doped hafnium oxide, magnesium-doped hafnium oxide,gadolinium-doped hafnium oxide, yttrium-doped hafnium oxide, orcombinations thereof over the titanium nitride material.
 18. The methodof claim 16, wherein forming an amorphous hafnium-based material overthe titanium nitride material comprises forming hafnium silicatecomprising from about 4.4 mol % to about 5.6 mol % silicon over thetitanium nitride material.
 19. The method of claim 16, whereincrystallizing the amorphous hafnium-based material to induce formationof a dominant crystallographic orientation comprises forming hafniumsilicate comprising a dominant (200) crystallographic orientation. 20.The method of claim 16, wherein forming a titanium nitride materialcomprising a dominant (111) crystallographic orientation comprisesforming a greater amount of the titanium nitride material in the (111)crystallographic orientation than in another crystallographicorientation.